Loud-speaker



Patented June 21, 1932 UNITED STATES PATENT orrics FREDERICK A. KOLSTERAND SIGUBD A. SOLLIE, OF PALO ALTO, CALIFORNIA, AS-

SIGNORS TO FEDERAL TELEGRAPH COMPANY, OF SAN FRANCISCO, CALIFORNIA; A

CORPORATION OF CALIFORNIA LOUD-SPEAKER Application filed October 30,1928.

This invention relates to sound reproducing apparatus and moreespecially telephone loud speakers.

To facilitate the production of low fre quency notes, it is expedient toso design a loud speaker that the sound waves propagated from .one sideof the diaphragm are obliged to travel a considerable distance beforethey can reach the opposite side thereof. This is usually accomplishedeither by providing a baflie-board of rather large area or by placingthe diaphragm in a cabinet. In either event it is quite essential thatthere be no substantial opening at or near the periphery of thediaphragm such as would provide a path of low impedance to sound wavesbetween the two sides thereof.

On the contrary it is very desirable (particularly when the loud speakeris mounted in a cabinet) to be able quickly and conveniently to withdrawthe speaker mechanism and diaphragm from the cabinet for adjustments andrepairs.

On the face of things, it appears that these two objectives are inimicalone to the otherbecause a tight oint ordinarily entails clamping orfastening devices which inherently impede removal and replacement.

From what has already been said it is apparent that the primary objectof this invention is to facilitate the removal and .reim plantation orreplacement of a loud speaker (and, if desired, its immediateappurtenances) and at the same time to provide for the effective sealinof the joint between diaphragm an d battle-board or cabinet wall withouthaving to exercise any special precautions or solicitude againstpossible leaks around the edge of the diaphragm and without having toresort to the use oftime consuming, fastening, or clamping devicesbetween the diaphragn'i and baffle-board or cabinet wall. This at firstappearance seems like a rather insignificant consideration. but to theservice man who is on many occasions obliged to repeatedly remove andreinsert loudspeakers during the course of making adjustments, suchfacilitations are of real importance.

In accordance with the present invention the object indicated isaccomplished by mount- Serial No. 316,038.

therein with definite assurance that the joint between the diaphragm andcabinet wall is properly sealed.

Referring to the drawing:

Figure 1 is a side elevational view of a loud speaker unit positionedwithin an enclosing cabinet, the cabinet being shown in cross section.

Fig. 2 is a plan view of the unit employed in the cabinet of Fig. 1.

Fig. 3 is a cross sectional detail illustrating the sound-proof jointbetween the periphery of the loud speaker tympanum and the cabi net.

There is shown in the drawing a conventional form of cabinet 10 withinwhich is positioned a unit or assemblage 11 comprising several pieces ofapparatus, the nature and function of which will be presently set forth.The front wall 12 of the cabinet forms a part of the baflie means aswill be explained, and the bottom member 13 forms a'support for theseveral pieces of apparatus designated as a whole by reference numeral11. The back of the cabinet is preferably closed by a hinged door 14,provided with an open screen 16 to permit ventilation. The front wall 12is provided vith an opening 18 for the emission of sound; and for thesake of appearance this opening may be covered by fabric 19 and grille21.

The various parts of the assemblage 11. are mounted upon the common basemember 22, which is preferably formed of pressed sheet metal with ahollow underside for the accommodation of the wiring. In the examplechosen for illustration, the apparatus mounted on the common. basemember includes a rectifying and filter system comprising a powertransformer 23, a filter choke 26, power supply socket 28, filtercondensers 27, gas discharge voltage regulator tube 29, a resistor 47,and an audio frequency amplifying system comprising an input transformer44, an amplifying vacuum tube 43 and an output transformer 46.

The loudspeaker which forms the principal element of the assemblage 11comprisesan electrically operated actuating, device 31 which is mountedupon base member 22 by means of a standard 32. This device is preferablyof the type having a magnetic field energized from a source ofrelatively continu ous current as for example rectified direct currentsupplied by the filter), and a movable armature coil for actuating thediaphragm or tympanum. Mounted upon the device 31 are arms 33 supportinga rigid ring Ring 34 serves as a peripheral support for the tympanum 36,which in this case is in the form of a cone. The center portion or apexof this cone is connected to the movable armature coil of device 31. Itis preferred that the major portion of cone 36 be made of comparativelyrigid material and that the periphery of the same be connected to supporting ring 34 by means of a comparatively flexible portion 37. Thisconstruction permits free vibratory movement of the cone roper.

With the loud speaker arrangement such as described above, anysubstantial opening between the periphery of cone 36 and the wall 12,would be likely to permit intermingling of the sound waves propagatedfrom the inner and outer sides of the cone, which would be apt to giverise to and cause apprcci able interference, the resultant productbeingdistortion or suppression of the lower frequencies, or both. The frontwall 12 together with other parts of the cabinet form baffle meanspreventing distortion due to such interfering waves; and this battlemeans is made fully effective by providing an annular ring 39 ofsuitable material interposed between the supporting ring 34 and frontwall 12. It is preferred that this material be compressibly resilient,as for example relatively soft felt, so as to always provide a tightseal irrespective of slight inaccuracies in the positioning of unit 11within the cabi net. Soft felt is also particularly effective because ofits sound absorbing properties. In the preferred construction this feltring is secured to the rigid supporting ring 34, although it might besecured to the rear side of the front wall 12. For example, as shown inFig. 3 the rigid supporting ring 34 is provided with an annular groove41 within which the felt ring 39 is adhesively secured, and the otherface of ring 39 is designed to seat in an annular recess 42 provided inwall 12.

The amplifier means for supplying amplified current variations to thearmature coil of electromotive device 31, has been represented by anamplifier tube 43 having its input circuit connected to the secondary ofan input transformer 44. Output transformer 46 serves as means forcoupling the output of amplifier tube 43 to the armature ofelectromotive device 31. The terminal connectors or binding posts 48permit connection to a standard broadcast receiver. The output circuitof the amplifier is energized and also a negative bias for its grid isprovided, by the rectifier and filter means.

The filaments of the rectifier and amplifier tubes can be supplied withalternating current from transformer 23. Suitable sockets are providedfor all of the tubes to permit their removal or replacement.

When the unit 11 is inserted in the cabinet 10, the felt ring 39 isfitted into the recess 42, and the base member 22 is fixed to bottomwall 13 as by means of screws 49. Considerable, latitude in the positionof the unit 11 is permissible as inaccuracies in alignment are taken upby the resilient felt ring 39. fit any time desired the entire unit canbe removed from the cabinet merely by removing screws or bolts 49, forinspection or for replacement. As long as the felt ring 39 is withinrecess 42, the cone is properly baffled to minimize distortion.

The present application does not claim broadly the use of a resilientsealing ring (that subject matter being covered by the aforementionedSollie application) but is limited to the use of a resilient sealingring or the equivalent thereof in combination with means forautomatically positioning the diaphragm structure with respect to thebafiieboard or cabinet wall whereby the joint between is closed upon theloudspeaker being inserted in the cabinetthe arrangement being such thatit is unnecessary to clamp the diaphragm against the baffle-board orcabinet wall.

I claim:

1. Aloud speaker comprising a bafile'wall having an opening for soundtransmission therethrough, a tympanum co-operatively associated withsaid opening, a base member adapted to be removably positioned within acabinet, a sound translating device mounted upon said base for actuatingsaid tyinpanum, and power supply means also mounted upon said base, thepositioning of said base member being effective to maintain theco-operative relation between said tympanum and said baffle-walh all ofsaid parts carried by said base being solely supported thereby.

2. A loud speaker comprising a base member adapted to be removablypositioned within a. cabinet, an orificed batl'leavall constituting oneface of said cabinet, a sound translating device mounted upon said base,power supply means, and audio frequency amplifying means, both of saidmeans being mounted upon said base together with said device, saidmounting being effective to maintain a suitable co-operative relation beably supported within the cabinet, a sound translating device mountedupon said base, a tympanum adapted to be actuated by said device, meansfor supporting said tympanum upon said base member, and a ring ofresilient material adapted to fill the space between the periphery ofthe tympanum and the baflle wall of said cabinet, said tympanum beingpositioned with respect to said baffle-wall solely by reason of itsfixed relation to said base member, all of said parts carried by saidbase being solely supported thereby.

4. A loud speaker unit adapted for use in a cabinet having a battle wallwhich is provided with an opening for transmission of sound, a basemember adapted to be removably supported within the cabinet, a soundtranslating device mounted upon said base member, a tympanum adapted tobe actuated by said device, means for supporting said tympanum upon saidbase member whereby said base member is effective to maintain a suitableoperative position in said cabinet of the tympanum with respect to theopening in the bafiie wall of said cabinet, all of said parts carried bysaid base being solely supported thereby.

5. A loud speaker unit adapted for use in a cabinet having a verticalbaflle wall which is provided with an opening for transmission of sound,a horizontal base member adapted to be removably supported within saidcabinet, a translating device mounted upon said base member, a tympanumadapted to be vibrated by said device, a rigid annular ring to which theperiphery of the tympanum is secured, means for securing said ring tosaid base member whereby it is disposed in a vertical plane, and in aposition to cooperate with said opening when the unit is disposed withinthe cabinet, and a resilient annular ring interposed between said rigidgasket and said baffie wall, all of said parts carried by said basebeing solely supported thereby;

6. A loud speaker unit adapted for use in. a cabinet having a verticalbafile wall which is provided with an opening for transmission of sound,a horizontal base member adapted to be removably supported within saidcabinet, a translating device mounted upon said base member, a tympanumadapted to be vibrated by said device, a rigid annular ring to which theperiphery of the tympanun'i is secured, means for securing said ring tosaid base member whereby it is disposed in a vertical plane and-in aposition to cooperate with said opening when the unit is disposed withinthe cabinet, and an annulus of soft felt interposed between said rigidring and said bafile wall, all of said parts carried by said base beingsolely supported thereby.

7. A loud speaker comprising a base and a baffle-board rigidly attachedthereto, a diaphragm the periphery of which is detached from andadjacent said baflle-board, a gasket of resilient sound absorbentmaterial sealing the space between said bafile-board and the peripheryof said diaphragm, supporting and actuating means for said diaphragm,and a secondary base resting on and removably attached to said firstbase, said secondary base carrying said diaphragm supporting andactuating means and serving to position said diaphragm adjacent saidbaffle-board, all of saidparts carried by said secondary base beingsolely supported thereby.

8. In a loudspeaker device, a horizontal base and a bathe-board rigidlyattached thereto, a diaphragm the periphery of which is detached fromand adjacent said baffle-board, a gasket of resilient, sound absorbentmaterial sealing the space between said bafile-board and the peripheryof said diaphragm, a rigid supporting structure and an actuating meansfor said diaphragm, auxiliary devices for energizing said actuatingmeans, and a secondary base, on which said diaphragm supporting andactuating means and said auxiliary devices are secured, removablyattaohed to said first base, all of said parts carried. by saidsecondary base being solely supported thereby.

9. In combination a battle-board having an opening therein, a baseremovably mountable in a predetermined space relation with respect tosaid baffle-board, a loud speaker mounted on said base, said speakercomprising an actuating mechanism and a diaphragm, a relatively rigidstructure circumscribing the periphery of said diaphragm, said structurebeing supported by said base and detached from said battle-board, and acompressible sealing member interposed between said structure and saidbafile-board, said sealing member being operable to complete asoundproof joint between said bafileboard and the periphery of saiddiaphragm, all of said parts carried by said base being solely supportedthereby.

10. In combination a cabinet having a wall. with an opening, a baseadapted to be removably mounted in said cabinet, a loudspeaker mountedon said base, said speaker comprising an actuating mechanism and adiaphragm adapted to be actuated thereby, and a supporting structure forsaid diaphragm carried by said base, the arrange ment being such thatsaid diaphragm is retained in a predet rmined fixed space relation withrespect to said base, and further that when said base is put into placein said cabinet said diaphragm forms a closure for the opening in saidcabinet wall without being attached thereto, and a compressible memberinterposed in the joint between the periphery of said diaphragm and saidcabinet wall, said compressible member being operable to seal said jointwhen said base is in its proper predetermined position in said cabinet,all of said parts carried by said base being solely supported thereby.

11. In a loudspeaker, a cabinet, a translating device comprising adiaphragm with supporting and actuating means therefor, a peripheralframe about said diaphragm, a resilient sound-proof gasket attached tothe base of said frame, an opening in the front wall of said cabinetsmaller than said peripheral frame, a larger opening in the rear of saidcabinet and a base to which said translating device is attached, saidbase being slidably insertable into said cabinet through the rearopening, whereby said diaphragm is positioned directly behind said frontwall without being attached thereto but with said gasket compressedagainst the wall and surrounding the opening therein, all of said partscarried by said base being solely supported thereby.

12. The combination of a conical diaphragm and apparatus for actuatingthe same, a cabinet one face of which forms a baffle-wall having anopening for transmission of sound, means comprising a base forremovab'ly supporting within said cabinet the conical diaphragm and itsactuating apparatus as a unit, means effective solely through the basefor retaining the position of said diaphragm with respect to saidbafliewall, a relatively rigid ring by which the periphery of saiddiaphragm is supported and a gasket of relatively soft materialinterposed between said rigid ring and said bafiiewall, all of saidparts carried by said base being solely supported thereby.

In testimony whereof, we have hereunto set our hands.

FREDERICK A. KOLSTER. SIGURD A. SOLLIE.

